Semiconductor devices are generally manufactured by furnishing a large diameter silicon wafer having IC circuits formed therein, dicing the wafer into semiconductor chips, bonding and securing under heat and pressure the semiconductor chip to a lead frame using a curable liquid adhesive or die bonding resin for mounting purpose, and wire bonding to electrodes, followed by encapsulation for handling and protection from the surrounding environment. Such encapsulation forms include hermetic packages such as metallic packages and ceramic packages, and non-hermetic packages using resins. At present, the latter packages based on resins, especially by transfer molding technique, are most common because of mass scale productivity and low costs. Despite such benefits, the resin molded packages are undesirably poor in moisture resistance, heat resistance, thermal stress relaxation and heat release.
In concert with the current demand for electric and electronic equipment of smaller size and more multi-functions, the interconnection technology of semiconductor devices seeks for a higher density and further miniaturization. Since semiconductor chips are increased in size, and semiconductor devices often take a chip scale package (CSP) structure having the same size as area array junction type chips free of lead frames or a chip stacked structure (stacked CSP or SiP), the packaging process poses more harsh thermal impacts or stresses.
The subsequent process of installing or mounting such semiconductor devices on printed circuit boards also imposes strict requirements as demonstrated by the reflow resistance enough to accommodate lead-free solders that reaches a high temperature of 265° C. There exists an increasing need for a material having optimum and high functions. Among package constituent materials, in particular, the die bonding resin has properties controllable over a relatively wide range and can be readily tailored to meet such requirements. Thus, a material having a high bond strength, a low modulus of elasticity and high heat resistance enough to withstand harsh thermal impacts or stresses is needed as the die bonding resin.
Miniaturization is also imposed on support substrates on which semiconductor chips are installed. The use of liquid adhesive has problems including contamination of electrodes with the adhesive which is squeezed out of the chip edge upon mounting of a semiconductor chip, and failure of wire bonding due to chip tilt caused by uneven thickness of an adhesive layer. There is a desire to have adhesive films that overcome these problems.
In the prior art, low modulus materials having siloxane structures incorporated into polyimides and polyamide-imides which are heat resistant resins were developed as the desired adhesive. For example, JP-A 5-009254 and JP-A 4-264003 disclose siloxane-modified polyamide-imides, which are less adherent to substrates.
JP-A 10-060111 discloses to combine a siloxane-modified polyamide-imide with a compound having at least two maleimide groups for improving high-temperature properties. This resin composition is less adherent.
JP-A 7-224259 and JP-A 8-027427 disclose heat resistant adhesive films comprising a polyimide silicone and an epoxy resin, having excellent adhesion, a low modulus of elasticity and heat resistance. In the course of packaging process, the bond of encapsulating resin to a die bonding adhesive layer after adhesive layer curing is very low.